1. Field of the Invention
The present invention relates to an automatic engine shutdown apparatus, and more particularly to an automatic engine shutdown apparatus for automatically shutting down an engine in view of the travel history of a vehicle.
2. Description of Background Art
Electric vehicles having a motor as a power source are environment-friendly and have good acceleration and deceleration responses. However, they have disadvantages in that their cruising distance is presently short due to a limited battery capacity and the unit cost of energy per traveled distance is high, making the electric vehicles less economic. Hybrid vehicles carrying a motor and an engine are put to practical use as eliminating the disadvantages and taking the advantages of the electric vehicles.
Generally known hybrid vehicles are classified into the series hybrid type, wherein only a motor is used as a power source of the vehicle and an engine is used as a drive source for a generator for charging a battery; the parallel hybrid type, wherein a motor and an engine are used as power sources of the vehicle and selectively operated depending on running conditions, etc.; and the series parallel type wherein the above two types are selectively used depending on running conditions.
Japanese Patent Laid-Open No. 2000-115908 discloses a hybrid vehicle technology for shutting down the engine when the accelerator pedal is not depressed, the vehicle speed is of a predetermined value or less, and the remaining charged capacity of the battery is sufficient, in order to reduce wasteful fuel consumption while the hybrid vehicle is at rest and also to reduce the emission of exhaust gases.
According to the related art described above, if engine shutdown conditions are satisfied based on the accelerator pedal state and the vehicle speed, the engine is automatically shut down unless remaining charged capacity of the battery is insufficient. In the related art described above, the travel history of the vehicle is not taken into account in shutting down the engine. When the hybrid vehicle runs on a jammed street, the engine tends to be repeatedly automatically shut down and restarted. If a standby time after an automatic engine shutdown condition is satisfied until the engine is actually shut down is set to a long period depending on the travel on the jammed street, then when the hybrid vehicle stops at a traffic signal, or the like, while running on a street with less traffic, the engine is not immediately shut down.